Telephone apparatus



Aug. 30, 1938. F. G. TROISI TELEPHONE APPARATUS Filed Aug. 29, 1955 2Sheets-Sheet l Patented Aug. 30, 1938 UNITED. STATES P TsNrorl-lcs F.....$Z." a. Application Aunut 29, 1935, Serial No. 38.408

The present invention relates to a telephone instrument intendedtofunction in a system as transmitter or receiver, independently ofexternal current sources, and constitutes a continuation in part of myapplication Serial Number 713,023

filed on February 26, 1934.

Due to inherent defects and general inefllciency, instruments of the socalled batteryless type heretofore constructed, have failed to meet withcommercial success. In most cases the diaphragms oi such instrumentshave been strained beyond desirable limits in an attempt to obtainmaximum amplitudes of vibration and a mini mum weight of the movingsystem. In attempts to balance the mechanical system, balance of themagnetic circuit has been overlooked with a resulting imperfection oisound transmission.

Units conforming to the present construction find application for anyinstallations wherein local telephone systems are used, such as forships. apartment houses, hotels, oifices, mines, factories, etc., aswell-as for submarine salvage as disclosed in the parent applicationalready referred to.

In use as a transmitter, the unit of the present invention derives itsactuating current from the sound vibrations impressed upon thediaphragm, obviating the need for batteries or other external currentsources. As a receiver, the unit converts the incoming electricalcurrents to sound waves which are reproduced by the diaphragm. Whileespecially intended for use without external current sources, theinterposition of a battery or other current source in the circuit isalso contemplated.

Faithful reproduction is obtained throughout the audio frequency rangewith units of the pres-= ent construction, by virtue of the proportionsoi the various masses and arrangements resorted to. Undue damping isavoided, and injury to the parts is prevented.

The armature oi? the electromagnetic circuit is supported in a trulybalanced condition, and measures are taken to preserve a balance of themagnetic circuit as a whole. v Sound vibrations impressed upon thediaphragm of transmitter or receiver alike, represent more nearly themean values, whereby distortion is overcome and the diaphragm issubjected to smaller strains than in known structures.

It is with the object of overcoming the faults of and irictionally heldthereby.

prior constructions and of attaining the ends,

already outlined, that the present invention is proposed, the details ofwhich will be understood from the following description in conjunctionwith the accompanying drawings,

Fig. 1 is a partially exploded view of the telephone unit;

Fig. 2 is a detail of portions oi the magnetic system, partially brokenaway.

Fig. is a sectional elevation taken along line 3-3 of Fig. 1 with theparts in assembled relation;

Fig. 4 is a portion of the section along line H oi'Flg. 1 with the partsassembled;

Fig. 5 is a plan view of the diaphragm;

Fla. 6 is a plan view of the partially assembled unit; and J Fig. 'i' isan. elevation showing one manner in which a pair oithe units may becombined as a set.

A diaphragm it is sandwiched between a spacing ring i Land an annularboss I2 which is integral with and protrudes irom a pertorated coverplate It, whereby an. air chamber is defined between the diaphragm andcover plate. The spacing ring it has a bearing upon a plate it whichserves as a support for the various elements. The base plate and coverplate are provided with registering openings and it respectively, forthe reception oi assembly screws. Another set 01' openings provided inthe cover plate are intended to receive screws for attachment toahousing, not shown, for enclosing the working parts in watertightcondition. a

Secured to the base plate it by-bolts I1, is the assembly for effectingthe induced current: in response to the voice or other sound frequenciesimpressed upon the diaphragm. This assembly comprises a permanenthorseshoe magnet i8, pole pieces IS, an armature 20, an armature housing2 I, a winding it properly insulated fromthe metallic structure, andmeans for holding the various elements in assembled relation andproperly spaced. A pinzt couples the diaphragm assem-- bly to thearmature. to which elements its rew spective ends are positivelyconnected, though ad- .justably, by solder or the like.

The bolts i'i have their heads countersunk in the base plate, theirshanks extending through thesarnewith a forced fit in order to maintainthem'in rigid, spaced relation. The spacing of these bolts is such, thatthe ends of the horseshoe magnet, it are nicely received therebetweehCounterboredopenings formed near the opposite ends oi the magnet,receive the screws 24 which threadediy engage the pole-pieces it tofasten the same to thepoles of the magnet. Each of the pole-pieces ispreferably termed from a flat sheet of magnetic material, which is outto a substantially T- u shape, the horizontal bar of the T tending toconverge at its extremities by virtue of a slight taper on its loweredge. In assembled relation, these pole-pieces each have a verticalportion contiguous to and coextensive with the poles of the horseshoemagnet. One end of each of these vertical portions (in Fig. 2' the upperend oi the left hand pole-piece and the lower end of the right handpole-piecel joins a horizontally extending portion which issubstantially coplanar with one of the planes of the horseshoe magnet.The tips of the pole-pieces are formed by folding inwardly towards theaxial plane of the permanent magnet, a pair of wings which constitutedthe horizontal bar of the original T. These wings or tips of therespective pole-pieces extcnu towards one another, but are maintained ina pre determined spaced relation by .a series of lugs t5 extending fromthe armature housing.

A light weight armature 20 of magnetic material, and substantiallyrectangular in plan, has a short perforated integral lug 25 extendingcentrally from one side thereof. Parallel to the side bearing the lug26, on a line passing through the center of gravity of the armature, apair of open ings are formed, symmetrical with respect to said center ofgravity, through which the ends of a supporting pin 21 are passed. Thepin is preferably a length of resilient wire having its ends bent at totheir base, forming a pair of parallel arms. The base of the pin ispermanently attached to the armature, as by soldering or thelikepindlcated at 2B.

The ends of the pin 21 are received in openings formed in the uppersurface of a one-piece armature housing 2| which is of rigid, lightnonmag netic materialfpreterably metal. The armature is centered in itshousing, whereupon the pin ends are riveted and aflixed to the housingby soldering or the like. The housing comprises a top surface, a pair ofside Walls perpendicular thereto, opposed base portions spaced from oneanother and parallel to the top surface, and carefully calibrated lugs25 projecting from both ends of both side walls, making four in all. Theupper and lower edges of all of these lugs 25 lie in two parallelplanes, for the purpose of spacing the pole pieces IS. The base of thehousing, being discontinuous, prevents to a large extent, the effects ofeddy currents.

Bridging the gap between the base portions of the armature housing,there is provided an insulating block 29, which in conjunction with itsinsulating wrapping 30, spaces the spool flanges 3| of insulatingmaterial, which are provided with elongated slots for the reception ofthe armature housing. Thus, except for its lugs 25, the armature housingserves as a core for the magnet winding 22 which is formed upon thewrapping 30 and between the flanges 3|. These elements are held inassembled relation by bending the four lugs 25 outwardly along theirline of junction with the housing proper. After the predetermined numberof turns of suitable guage wire have been applied on the spool, aninsulating covering 32 is wrapped about the coil so formed.

A clamping bar 33 of non-magnetic material is provided with openings forthe reception of the threaded ends of the bolts H, for clamping theassembly to the base plate upon application of the nuts 34. The bar isprovided with a pair of locating pins 35, preferably pressed from thematerial '01 the bar itself, which pins are received in a pair ofcooperating openings in the upper I surface of the magnet. Also, the barpreferably bowed downwardly at its central pi rtlon so as to resilientlybear against the horizontal portion of the upper pole-piece 3B. Thelower polepiece is also given a definite bearing surface against thebase plate by designing the latter in the manner shown in Fig. 6. Thecentral aperture of the base plate is formed of two concentricsemi-circles of different radii. Thus the smaller semi-circle 37! leavessufiicient material to suppm" "t the pole-piece without unduly dampingthe di While the larger semi-circle it provides a sufficiently largepassage r air within the instrument so as not to interfere with itssensitivity and operation.

As shown in Fig. 4, the armature preferably terminated in the planes ofthe poleiece surfaces so as to be cut by substant flue: emanatingtherefrom. To p age through fatigue, the armature lug as short aspossible, and to allow for ie solder or the like applied thereto forholding the pin .25], the rear surfaces of the pole-pieces are providedwith grooves 40. A further and more important function of these grooves,is the balance of the magnetic system which is achieved thereby. Theprojecting lug 25 tends to decrease the reluctance of the gap at therear of the polepieces, which factor is compensated by reducing the areaof the pole faces at this point. Consequently, the torque applied at theopposite sides .of the fulcrum provided by the pin 21 will be equalizedand likelihood of distortion dimh'lished.

After the diaphragm i0 is clamped into position, the pin 23 isinserted'through the opening in the lug 26, and with the armatureassigned to its final neutral position with respect to the opposed poletips, the pin is fixed to the lug. Should the diaphragm subsequentlybecome bent, or should there be need of adjustment for another reason,the pin may be readjusted with respect to the armature lug and a newjoint formed.

The ends of the winding 22 are brought out to a suitable terminal block41, from which they are connected to their respective conductors forcompleting a circuit with one or more similar units.

The diaphragm I0 is preferably a thin disk of resilient flexiblematerial, such as duralumin, highly responsive to voice frequencies,which in the form shown, has been impressed with a series of concentriccorrugations, the spacing and depth of which in general, increase astheir diameters decrease.

Whereas it is usual practice in devices of this type to solder orotherwise connect the center of the diaphragm directly to the pin whichtransmits the movements to or from the armature, more reliable andgenerally better reproduction has been obtained in this construction bytransmitting movements between diaphragm proper and the pin through anintermediate, substantially rigid member which is supported at aplurallty of points on the diaphragm. To prevent undue damping of thediaphragm, this member is attached at the peak of a corrugation, beingotherwise out of contact with the diaphragm.

This connecting member 42 which is preferably of light yet rigidconstruction, has a body portion of substantial cone shape, terminatingat its base in a rigldifying bead 43, extending from which, there are aplurality of short stiff lugs 44 which are perforated for the receptionIll) of rivets 45 for attachment to the diaphragm 76 a waterproof andplastic material such as a wax is applied over the solder.

As shown, three lugs connect the member 42 with the diaphragm, thisnumber having been chosen as a-balance between light weight .andrigidity, both of which factors are important. Whether the movements aretransmitted from the diaphragm to the armature while the unit serves asa transmitter, or from the armature to the diaphragm when in use as areceiver, a more nearly perfect reproduction is effected than with a.pinconnected at a single point to the center of the diaphragm. Thenumber of such lugs may be varied without departing from the spirit ofthe invention.

The air chamber between the diaphragm and the diaphragm cover isdesigned with respect to the moving system, that is, the diaphragm, itspin and the armature, so that when a. plurality of the units areconnected in a circuit, the circult will be substantially uniformlyresponsive to frequencies throughout the audible range. The resonance ofa unit used as a receiver will be difierent than when it is used as atransmitter, due to a change of its effective air cham-- her, and thenumber of different resonant frequencies of the system will beincreased, tending to render uniform the output of the system over theentire audible range.

As appears inFig. 3, the length of the pole tips is necessarily slightlygreater than the length of the armature housing for the lugs to performtheir function of spacing these pole tips uniformly.

These telephone units operate as transmitteror. receiverinterchangeably. and due to their construction, operate emciently underthe high pressure conditions to which they are frequently subjected asin under water salvage operations when used as a transmitter, thevibrations of the diaphragm set up by the voice, are imparted to thebalanced armature through the pin a. The movements of the armature inthe field of the permanent magnet, vary the reluctance of the magneticcircuits with a frequency proportional to that of the sound wavesproducing these movements. Accordingly, proportional currents will beinduced in the winding, which currents will be carried to similar unitsserving for the instant as receivers. When current flows in the receiverwinding, magnetic flux will be produced to oppou or reinforce that ofthe permanent units especially adaptsthem to use in connection withsubmarine salvage apparatus, they have been highly successful in otheruses and their application is not to be restricted beyond the scope ofthe appended claims.

I claim:

1. A telephone unit comprising a permanent magnet carrying a pair ofdetachable pole pieces, an electromagnet embraced by said pole pieces,said electromagnet comprising a spool having separate flanges and adiscontinuous one-piece sheet metal armature housing having elementsholding said spool in assembled relation and projecting between saidpole-pieces and in contact therewith for limiting the positions of thelatter.

2. A telephone unit comprising a permanent magnet carrying a pair ofpole-pieces, an electromagnet embraced by said pole-pieces, saidelectromagnet comprising an armature and a. one-piece sheet metalhousing therefor, a spool composed of a plurality of elements formedabout said housing, said housing carrying lugs engaging and holding thespool in assembled relation and contacting said pole-pieces for spacingthe latter.

3. A telephone unit comprising a base plate carrying a pair of spacedbolts, a horseshoe magnet carried by said base plate having its legs infrictional engagement with said bolts, pole-pieces carried by saidmagnet having surfaces coplanar with those of the magnet and a clampingbar receiving said bolts ensasins coplanar surfaces of said magnetand-said pole-pieces for. clamping the same to said base plate. v

4. A, telephone unit comprising a horseshoe magnet having a pair ofoppositely directed polepieces rigidly attached thereto, saidpole-pieces having surfaces coplanar with those of the magnet, aclamping bar engaging the upper surfaces of a pole-piece and the magnetand having positioning pins received by apertures in the magnet,

a base plate engasing the lower surfaces of a HORENTmO G. 'I'ROISI.

